This invention relates to an improved process for the recovery of 2,6-dimethylnaphthalene. More particularly, this invention relates to an improved method for separating 2,6-dimethylnaphthalene (hereinafter "2,6-DMN") from hydrocarbon mixtures containing isomers of 2,6-DMN, e.g. 2,7-DMN; 1,7-DMN; 2,3-DMN, and the like by selectively forming a clathrate complex of 2,6-DMN with purified m-nitrobenzoic acid (hereinafter "m-NBA").
It is known from U.S. Pat. Nos. 3,725,490 and 3,812,198 that 2,6-DMN may be separated from mixtures containing its isomers, particularly 2,7-DMN, by first selectively forming a complex of 2,6-DMN with nitrobenzoic acid, separating the complex from the reaction mixture containing the DMN isomers, and then breaking the complex to yield a concentrated or purified 2,6-DMN. Conventionally, formation of the complex, particularly when the feed mixture only contains 2-3% 2,6-DMN, and room temperature is employed, is preceded by an induction period of up to 30 minutes or more, followed by sometimes longer periods of complex formation which yield only relatively small percentages of hydrocarbon.